好吧,我有一个有三个表的数据库. Q& A,类别和ID.类别包含类别,Q& A具有问题和答案,ID具有各种类别的ID以及附加的问题.如何从数据库中提取以便获得一个类别,然后是一个属于该类别的Q& A循环？

function PRint_categories() {
global $MysqL;


if (($categories = $MysqL->select_all("SELECT * From QandA_wiki.categories")) !== false) {
foreach ($categories as $cITem) {
$counter = 1;
print"<div id=\"categories_start\" style=\"width:424px; margin:0 auto;\">\n";
print"<div id=\"category\" >\n";
print"<h2> {$citem['description']}</h2>";
print  "<div class=\"col-lg-12 footerLine\"><hr /></div>";
    if (($questions = $MysqL->select_all("SELECT * From QandA_wiki.qanda")) !== false) {
    foreach ($questions as $qitem) {
        print"<div id=\"question_number\" >\n";
        print"<div id=\"questions\" >\n";
        print"<p>#: {$counter} -<strong>{$qitem['question']}</strong></p>";

        print"</div>\n";
        print"<p>     {$qitem['answer']}</p>";
        print  "<div class=\"col-lg-12 footerLine\"><hr /></div>";


        print"</div>\n";

        print"<div style=\"clear:both;\"></div>\n";
        print"<br />\n";
        $counter=$counter+1;
        }
      }
print"</div>\n";
print"</div>\n";

print"<div style=\"clear:both;\"></div>\n";
print"<br />\n";

}}}}

SELECT QandA_wiki.qanda.*,QandA_wiki.qanda.id,QandA_wiki.qanda.name_of_your_column
FROM QandA_wiki.qanda
LEFT JOIN QandA_wiki.categories
ON QandA_wiki.qanda.category_id = QandA_wiki.categories.id // This is a guess here...likely will need to modify
WHERE QandA_wiki.categories.name_of_your_column = name_you_want; // This where clause does the filtering as you needed

$query = MysqLi_query($link,"SELECT QandA_wiki.qanda.*,QandA_wiki.qanda.name_of_your_column
    FROM QandA_wiki.qanda
    LEFT JOIN QandA_wiki.categories
    ON QandA_wiki.qanda.category_id = QandA_wiki.categories.id
    WHERE QandA_wiki.categories.name_of_your_column = name_you_want;");